Climate Change

Abstract

Weather can change many times a day. Climate.the sum of weather.changes slowly, over decades and centuries, but it can change abruptly with large volcanic eruptions, instabilities in ocean currents, or meteorite crashes. The dramatic 1815 Tambora eruption spewed 100 km3 of ash, causing “a year without a summer” to cool Earth by 4°C. Cooling from volcanic and anthropogenic aerosols must be factored into climate predictions.Without industrialization, Earth’s temperature is raised 33°Cby greenhouse gases [water vapor (21°C),CO2 (7°C), other gases (5°C)]. The Intergovernmental Panel on Climate Change (IPCC) projected in 2002 an additional 2.5°Crise (1.4.5.8°C) for a doubledCO2 (560 ppm). Positive feedback magnifies warming. For example, increased CO2 warms Earth, which increases atmospheric moisture that further raises Earth’s temperature. Positive feedback also comes from reduced snow and ice, which reduce solar reflection. Increased cloudiness has a negative feedback since increased numbers of high-altitude clouds increase solar re- flection. But more low-altitude clouds also produce positive feedback by trapping infrared radiation. The height of the clouds is critical in this comparison.